Anyone had this allison problem

[f7pilot]

I have an 02 duramax(twice the 6.5 motor) 3500 and my transmission is shifting slow or won't shift from park. My prndl indicator shows a blinking 3 but won't go.

I have about 105,000 miles on it and run amzoil tranny fluid.

Anyone with any help would be appreciated.

Thanks in advance.

[bluenote]

It sounds like a bad NSBU switch to me. When mine went out at a little over 90K miles, the gear indicator lights would blink, it wouldn't always engage gears, etc.... I was able to get it covered as a warranty item because GM considers it an emissions issue when your Allison is paired with a diesel engine. You may or may not get the same thing since you are over 100K. You can change them yourself, or at least find an Allison shop versus a GM dealer to get the job done for less. Good Luck!